Fixatives

Question 1

What are the 4 main characteristics of Formaldehyde?

Answer 1

• Tolerant
• Rapid
• Non-coagulant
• Additive agent

Question 2

What is the difference between a coagulant and non-coagulant fixatives ?

Answer 2

Coagulant:
- Harsher
- Direct at proteins
- Permits better penetration through the tissue
Non-coagulant
- Gentler
- form gel like compound
-Fewer artifacts

Question 3

What is the difference between an additive and non additive agent?

Answer 3

Additive:
- alters electrical charge
- adds themselves to the tissue
Non-additive
- precipitate/ coagulate the protein
- don’t attach to the tissue
- effect H+ bonds
- Ethanol the only one

Question 4

What is the difference between tolerant and non tolerant?

Answer 4

Tolerant:
- Tissues can be exposed for a long time without adverse effects.
Non-Tolerant:
- Tissues cannot be exposed for a long time without adverse effects.

Question 5

How does formaldehyde react with proteins?

Answer 5

Mainly reacts with the side amino groups (NH2)
-forms methylene bridges
- prevents alteration during processing and staining